The predominant microorganisms in the advancing front of rapidly destructive periodontal diseases are gram negative anaerobic rods and spirochetes. The proposed work centers on the antigenic relationships in four groups of these gram negative anaerobes which have been isolated at the Forsythe Dental Institute and at Case Western Reserve University from patients with periodontal disease. The groups include 1) a newly proposed genus of translocating bacteria, Capnocytophaga; 2) a "vibrio-corroding" group of short rods which includes members of the genera Campylobacter, Eikenella, and Bacteroides; 3) a group of Fuso-bacterium nucleatum subspecies; and 4) a group of Bacteroide-like organisms. Strains from each of these groups have been shown to be periodontopathic in germ-free rats. Antisera will be raised in rabbits against live or formalinized cells. Cross reactions between groups and within groups of organisms will be studied by cell wall agglutination, agar double diffusion and indirect fluorescent antibody (IFA) techniques. An attempt will be made to define serogroups of biochemically and morphologically related organisms. If necessary, antisera will be prepared against isolated cell wall antigens. The goal is to produce specific antisera which can be utilized to identify the above organisms on primary isolation by use of the IFA technique. Such a capability will facilitate studies in the development of subgingival plaque and periodontal disease.